MOSCOW - Russia on Monday officially registered incumbent Vladimir Putin as a candidate for the presidential election in March, a vote that he is all but certain to win. The 71-year-old has led Russia since the turn of the century, clinching four presidential ballots and briefly serving as prime minister. The election will be held over a three-day period from March 15 to 17. Putin’s spokesman, Dmitry Peskov, told Russian media on Monday the longtime leader would not take part in pre-election debates.